Effects of particle size and interfacial slope structure on the mechanicaland fracture properties of PVC filled with crosslinked PMMA particles

The effects of interfacial structure and particle size on the mechanical pr operties of an particulate-filled composite have been investigated using a model system. For this purpose, uncrosslinked and crosslinked poly(methyl m ethaerylate) particles having the mean size of about 0.8 mum are prepared b y a seeded emulsion polymerization, and then the amount and the distributio n of crosslink points in the particles are varied. The obtained emulsion pa rticles are powdered by a freeze dry method and dispersed into poly(vinyl c hloride) matrix by a melt blending. The uncrosslinked particles are complet ely dissolved in the matrix due to a good compatibility of poly(methyl meth acrylate) with poly(vinyl chloride). In the case of the crosslinked particl es, the mutual diffusion of the polymer molecules is restricted within the particle/matrix interfacial regions by the crosslink points. The interfacia l structures with different concentration slope dependent upon the amount a nd the distribution of inner crosslink points are developed with the same p article size. It is found that the yield stress decreases with a decrease i n the interfacial adhesion. Furthermore, the effect of particle size is con firmed in the weakest interfacial adhesion system in the range of 0.3-0.8 m um. When the interfacial adhesion is sufficient or the particle size is eff ectively small, the yield stress was never lower than those of their compon ents.